The present invention pertains to a surgical prosthesis designed to remedy the cartilage wear in the patella and femoral trochlea of the human knee.
The knee includes the femoro-tibial joint, as well as the femoro-patellar joint.
The upper part of the patella is continued by the quadriceps and the lower part is connected to the tibia by the patellar tendo. The patella is connected with the femur, on its lower and external sides, by the marsupia patellaria.
Under the combined efforts produced from the quadriceps, the patellar tendo and the marsupia patellaria, the patella is subjected to an effort applied on the femur, and more particularly on the cartilage of the femoral trochlea.
Cartilage wear can therefore be noticed in the patella or the femoral trochlea of various individuals. The well known Mac Keever prosthesis is a partial prosthesis and consists of a kind of metal shell designed to cover the rear side of the patella, while sliding against the trochlear cartilage.
The femoro-patellar options offered by the Freeman and Gunston prosthesis are also well known.
Another popular model is the Bechtol full prosthesis, which is a symmetrical prosthesis including a metal trochlear element and a polyethylene patellar element with tilt adjustable edges.
The disadvantage of these types of prosthesis is that they cannot be adapted to the case of isolated femoro-patellar arthrosis with fixed, partial dislocation of the patella. Indeed, the treatment of this lesion requires four conditions which consist of the surface replacement, the alignment of the patella with the femur, the adaptation of the prosthesis to the deformation of the osseous parts concerned and the provision for a sufficient, undamaged spot in case of failure, so as to make a correction possible.
Some well-known prosthesis meet the first two requirements, but their adaptation to the sometimes significant deformations of the trochlea may be uneasy; moreover, in case of failure, their removal may reveal a surface which is damaged to the point that the efforts produced by the quadricipital tendo, following patellectomy, may no longer be tolerated. These disadvantages are suppressed by the present invention inasmuch as the device adapts itself to the deformation of the osseous parts.